Prior Art
U.S. Pat. No. 5,493,190 issued to Mueller on Feb. 20, 1996 and entitled Windshield Wiper Auto-Delay Control Interface, teaches the use of resistors to control the voltage applied to a node in a windshield wiper control for an auto-delay interface.
U.S. Pat. No. 5,239,244 issued to Teder on Aug. 24, 1993 and entitled Vehicle Interface for Moisture-Sensitive Wiper Control teaches a means to facilitate integrating a moisture-sensitive wiper control system into an existing design of wiper system with minimum impact on manufacture and retrofit.
U.S. Pat. No. 4,947,092 entitled Solid State Windshield Wash and Wipe Controller issued to Nabha et al. on Aug. 7, 1990, teaches short circuit protection for the solid state motor driving and braking control for a plurality of modes of operation of the windshield wipers.
U.S. Pat. No. 4,857,815 entitled Switch for Energizing an Electric Motor of a Wiper System issued on Aug. 15, 1989 to Erdelitsch et al. teaches a wiper switch design for energizing an electric motor of a wiper system. In addition it teaches the use of bridging contacts in the switch.
U.S. Pat. No. 4,620,141 issued to McCumber et al. on October 1986, teaches an electronic control circuit for a windshield wiper motor that includes a windshield mounted sensor module utilizing a plurality of radiant energy sources. These sources are pulsed on and off in accordance with a pre-established duty cycle, in conjunction with a further plurality of radiant energy sensors which are oriented relative to light transmitting channels such that they intersect at the outside surface of the windshield.
U.S. Pat. No. 4,339,698 issued to Kearns on Jul. 13, 1982 and entitled Control Apparatus for Windshield Wiper System, teaches an apparatus for controlling the operation of a windshield wiper motor using resistors connected from the switch. The switches are single pole double throw switches.
U.S. Pat. No. 4,317,073 issued on Feb. 23, 1982 to Blaszkowski and entitled Windshield Wiper Control System, teaches a moisture sensing windshield wiper circuit. Resistors are liberally used in the timing circuits.
U.S. Pat. No. 3,869,654 entitled Windshield Wiper Control Circuit and issued on Mar. 4, 1975 to Bischoff et al., teaches windshield wiper control for a pulse and intermittent run system using resistors in the operator control wiper switch.
Presently, an interval wiper subsystem has a wiper switch that is currently part of the multifunction switch, a control module and a wiper motor. The wiper switch is used by the operator to control the speed of the wiper motor and the dispensing of washer fluid for the windshield or liftgate. The use of the wiper switch allows the operator to select the mode of the wiper motor, OFF, INT1, INT2, INT3, LOW and HIGH. The wiper switch also allows the operator to dispense washer solvent onto the windshield or liftgate with the amount controlled by the length of the time the washer button is actuated or depressed.
The wiper switch modes that control the wiper subsystem use many different principles. A traditional method uses direct control of the `LOW` and `HIGH` speeds of the wiper motor requiring high current contacts in the wiper switch and a variable resistor for the interval mode which provides control to the wiper motor via a control module. Subsystems using this approach require five to ten wires from the wiper switch.
A variation on this method utilizes relays to control the `HIGH` and/or `LOW` speeds of the wiper motor, lowering the wiper switch current and potentially reducing the number of wires from the wiper switch.
Another method uses a resistor ladder with as few as three wires and however, must use electronics to decode the voltage levels from the wiper switch to provide control to the wiper motor. However, this method is susceptible to leakage current, switch corrosion and manufacturing issues impairing performance.